Steerable assembly for wheelchairs and the like

ABSTRACT

A STEERABLE ASSEMBLY FOR WHEELCHAIRS, MOVABLE BEDS AND LIKE DEVICES ADAPTED TO BE MOVED ACROSS THE GROUND OR FLOOR ON ROLLERS. THE ASSEMBLY HAS A PAIR OF UPRIGHT TRANSVERSELY INTERCONNECTED TUBULAR POSTS AT THE BOTTOM OF WHICH ARE PROVIDED CASTER ROLLERS IN RESPECTIVE BIFURCATED CASTER SUPPORTS OR FORKS. WITHIN THE LATTER, BIFURCATED SPRINGS CAN BE DEFLECTED IN OPPOSITE DIRECTIONS TO ENGAGE THE POST AND THE ROLLER PERIPHERY TO IMMOBILIZE THE SUPPORT AND THE ROLLER WHEN AN ACTUATING MEMBER IS SWUNG FROM POSITION TO ANOTHER. THE ACTUATING MEMBER FORMS A TOGGLE WITH A CROSSBAR MEMBER AS IT IS DISPLACED THROUGH A DEAD-CENTER POSITION AND HAS A PAIR OF PINS AT ITS ENDS WHICH ENGAGE, THROUGH SLOTS IN THE POSTS, RESPECTIVE SLIDES CONTROLLING THE SHAFTS WHICH OPERATE THE BIFURCATED SPRINGS.

[ 1 June 28, 1974 STEERABLE ASSEMBLY FOR WHEELCHAIRS AND THE LIKE [75]Inventor: Friedhelm Miiller,Tonisheide,

Germany i [73] Assignee: Firma Happe & Co., Tonisheide,

Wulfrather Str., Germany 221 Filed: May22, 1972 21 Appl. No.: 255,448

[30] Foreign Application Priority Data Germany 16/35 1,564,850 3/1969France 16/35 Primary ExaminerBobby R. Gay Assistant Examiner-Doris L.Troutman Attorney, Agent, or Firm-Karl F. Ross; Herbert Dubno 5 7ABSTRACT A steerable assembly for wheelchairs, movable beds and likedevices adapted to be moved across the ground or floor on rollers. Theassembly has a pair of upright transversely interconnected tubular postsat the bottom of which are provided caster rollers in respectivebifurcated caster supports or forks. Within the latter, bifurcatedsprings can be deflected in opposite directions to engage the post andthe roller periphery to immobilize the support and the roller when anactuating member is swung from one position to another. The actuatingmember forms a toggle with a crossbar member as it is displaced througha deadcenter position and has a pair of pins at its ends which engage,through slots in the posts, respective slides controlling the shaftswhich operate the bifurcated springs.

14 Claims, 12 Drawing Figures ?ATENTEBJM28 W4 1820, 1 90 SHEET 5 OF 5iii .7

STEERABLE ASSEMBLY FOR WHEELCHAIRS AND THE LIKE FIELD OF THE INVENTIONMy present invention relates to steerable assemblies for wheelchairs,hospital beds, walking frames, convalescent, prosthetic and likeappliances or apparatus in which a pair of swivelable or steerablewheels rest upon the floor. More particularly, the invention relates toimprovements in a manually actuated mechanism for arresting thesteerable wheels in such devices.

BACKGROUND OF THE INVENTION In wheelchairs, movable beds such ashospital beds and convalescent beds, walking frames and like medicalappliances and other apparatus or devices adapted to roll along theground, it is customary to provide at least two steerable casters whoserollers engage the ground and support the assembly. Such additionalassemblies of this type may be provided and a single assembly of twocasters may be used with other propel-.

ling means. The term steerable is used herein to refer to a rollerarrangement which can be displaced angularly about an upright axis whenthe assembly movement suffers a direction change. It is not necessarywithin this definition to provide means for, individually swinging eachroller about the upright axis and the steering movement may be a resultof entrainment of the assembly by the remainder of the structure in awheelchair or the like in which the main wheels may be operated manuallyor automatically and steering accomplished by varying the rates and/orsense of rotation of the main wheels.

It is also a common practice, especially in wheelchairs and likeappliances, to provide means for arresting the casters so as to retainthe assembly in place. Since each caster arrangement is swingable aboutan upright axis and ,carries a roller which is journaled about agenerally horizontal axis, the arresting means should immobilize boththe caster support and the roller.

Where wheelchairs and like structures with frames are provided, thecasters may be disposed at the feet of respective posts or legs whichareinterconnected by a crossbar arrangement. A conventional actuatingsystem for an appliance of this type makes use of a handle controllingthe arresting means and operating a member extending through thecrossbar. This system has the disadvantage that additional means must beprovided to retain the handle in its locking and unlocking position.Also mounting the crossbar and the actuating system contained therein isdifficult and expensive and the system has been found to fail frequentlyin practice as a result of jamming within the crossbar. Finally, thearrangement of the actuating mechanism at least in part within thecrossbar interconnecting the two posts results in excessive wear of themoving parts.

It should be noted also that conventional systems using actuatingmechanisms within a crossbar have customarily employed cable devices forforce transmission between the actuating and actuated elements of thearresting mechanism. Such cable arrangements are prone to wear,difficult to repair and frequently unreliable.

OBJECTS OF THE INVENTION It is the principal object of the presentinvention to provide an improved assembly with steerable wheels orrollers which avoids the aforementioned disadvantages.

provide an improved low-cost arresting mechanism for a steerableassembly of the class described.

SUMMARY OF THE INVENTION These objects and others which will becomeapparent hereinafter are attained, in accordance with the presentinvention which provides a steerable assembly comprising a pair oftransversely interconnected tubular posts, each of which comprises arespective vertically shiftable shaft operating an arresting mechanismwithin the caster support to lock the latter against rotation about therespective upright axis and to lock the associated roller againstrotation. According to an important feature of the invention, a crossbarinterconnects the posts and cooperates with the actuating member whichalso transversely bridges them but is located externally of thecrossbar. The posts are provided with respective vertically extendingslots through which pins of the actuating member may pass to act uponthe respective shafts, the latter being biased by springs within theposts such that the srpings also act to hold the actuating memberagainst the crossbar in a toggle joint when the actuating member isshifted past a dead-center position to displace the pins.

More generally, where the crossbar member and the actuating member lieparallel to one another and are usually horizontal, the actuating memberis angularly displaceable about an axis transverse to the upright axesof the posts between two positions with different spacings of thetransverse axis from the crossbar member. One of the members, generallythe actuating member or a part thereof is displaceable relative to theother member (usually the crossbar member) along the posts to actuatethe pins, shafts and arresting devices as described. The actuatingmember in all cases, however, operates toggle-fashion for self-lockingor movement into a position in which the spring acts againstselfdisplacement of the actuating member in one position of thearresting mechanism. The toggle arrangement may make use of a bent-leverconstruction of the actuating member.

The resulting arresting mechanism for the steerable assembly isparticularly suitable for use with the steerable wheels of a wheelchairsince it allows handles on the actuating member to extend from eitherend thereof, i.e. on opposite sides of the wheelchair. The assembly islight, requires little room and can be exposed to considerable stresswithout damage. Since the toggle system uses the interfltting orinterengaging relationship of a fixed crossbar with a swingableactuating bar, no complicated indexing arrangement is required andoperation of the device is particularly simple. Furv 3 v thermore, sincethe actuating member or a part thereof cradles the crossbar member inthe locked position and a displacement along the post is necessary tobring the actuating member through the dead-center position to releaseit, there is'no danger that the arresting mechanism will beinadvertently released.

According to the present invention, therefore, an arscribed provides aconnecting member externally of the crossbar interconnecting the postsand havinga pair of slide bodies therewithin which are actuated by pinsextending through slots of the posts, the slots running in the verticaldirection or parallel to the vertical axes of the posts. As theactuating member is swung about an axis, which may correspond to the.axis of the crossbar ormay be spaced therefrom, portions at the ends ofthe actuating bar, eccentrically carrying the pins, shift the latteraxially of the posts to operate the arresting members. The actuatingmember thus constitutes amechanism for translating angular displacementabout a generally horizontalaxis into vertical displacement of the slidebodies along the vertical axis of the post,

,The actuating member is shaped as a bent lever or toggle having atleast a portion cradling the crossbar in the position of the actuatingmember in which it is to be retained. The actuating bar may be providedwith a pair of laterally projected handle portions which can bemanipulated by a patient in the wheel chair on either side with ease.Furthermore, the: handle portion may constitute the part of theactuating assembly forming the cradle with the actuating bar or may beseparate from the cradle member when the latterconstitutes a toggle linkof generally circular segmental configuration. Since the actuating barconnecting the two handle portions lies externally of the crossbar 'between'both legs of the wheelchair, i.e. between both: legs of the wheelchair, i.e. between both tubular posts, the cross-7 bar, the actuatingbar and thelegs can be substantially flush (without protruding members)except for the lat erally projecting handles. The toggle, bent-leveroreccentric construction allows the actuating memberrto rest against thecrossbar so that the former is retained Of course, the crank may also belocated below the crossbar whereupon the actuating member draws theslide against the force of the spring when: the actuating member shiftedthrough the dead center position. in the orientation of the crank abovethe crossbantof course, the springmay' simply be relieved topermit it ito operate the braking element. resting mechanism for an assembly of thecharacter dec According to a further feature of the invention, the.handle portions may be interconnected by a bar located externallyof thecrossbar as previously noted while the handle portions are rotatableabout the axis of the crossbar thereon and carryinglink elements operating the pins. The link elements, in this case; form the togglearrangement. According to yet another fea ture of the invention, theconnectingbar-between the handle portions constitutes a sleeve coaxiallysurrounding the crossbar and rotatable thereon, the connecting bar beingindirectly tied' to links as noted.

DESCRIPTION or THE DRAWING The above and other objects, features andadvan tages of thepresent invention will become more readily FIG; 4 isacross-section taken along the line lV IV V r of FIG. 2;

FIGLS is a vertical section through an assembly according to anotherembodiment of the invention with the parts in their braking position;

FIG. 6' is a sectionof the assembly of FIG. 5 with the 7 parts in theirreleased position;

FIG. 7 is a section taken along the line VlI Vllof FIG. 5; I

in placein a selfretaining manner without any addi-t V tional indexingmeans.

According to a more specific feature of the il'lVEfltion, the actuatingbar bridging the two postsis formed as a simple crank with offset endportions, the latter being constituted as side plates or linked thecrank-- and carrying the pins'The slide body within eachpostpre'ferably'forms a seatfor'acompression-typecoil;

spring which acts throughtthe pins andiside'platesor, cheeks of thecrank. to retain the latter sin fitsgselfii locking position againstthecrossbar afterthe'crank has been shiftedthrougha dead-centerposition'i Toaone side, of this dead-center'position, correspondingftoa,

first actuating position of the slide body andptheishaft upon which itacts, the spring functions' to;urge the,

braking member into engagementawith the post andlor the roller tolockthe caster against movementlathe other position, eg the positioncin,which the actuating member is selfretain'ed against the crossbar, thespring is stressed and the locking elements are relieved. The springthus acts as a so-called braking spring to hold the brake in an engagedcondition. The crank or actuating member can then be located above thecrossbar which may have a collar rotatably engaged by the actuatingmember to facilitate movement of the crank thereover.

Fit). 8 is a vertical section through the posts or legs of a wheelchairaccording to anotherembodiment of V the invention;

FIG. 9 is a detail view of a portion of the latter assembly in thebraking position of the parts,

FIG; 10 is a cross-sectional view taken along the line X X of FIG. 8;

FIG. 11 is a ,fragmental sectionof theactuating LY mechanism accordingto yet another embodimentof thev invention; and I FlGull is a sectiontaken- "alongthe line: X111} X]! M ems. 11.2

srsc ricnss mmo a 7 in FIG. '1 of the drawing; 1; milestones softener Ia; wheel chairgwhich is; provided wit'hthe caster assent bly: according;to; the invention. The wheel chair'com priseslfourlegsorpostsrformingatubularflank onlythe two from posts of which; have beenjnusnatedat -1. and 1 the pins by semicircular journaled. The assembly,according to the present invention, is designed to lock the casterarrangements 4.

Each of the caster arrangements 4, as also will be apparent from FIG. 1,comprises a bifurcated caster support or fork 7, the arms 7a and 7b ofwhich receive the rubber-tire wheel 6 between them. The wheel 6, alsoreferred as a roller, is journaled on an axle 6 between the arms 7a and7b of the fork as is customarily the case.

From FIGS. 1 through 4 it will also be apparent that the individualcaster arrangements 4 comprise two sets of ball bearings 8 and 9flanking and inwardly extending flange 7c of the fork and disposed ontop and on the bottom of the latter. The upper bearing cage 11a iscarried by a guide sleeve 11. The lower cage 11b forms an apron on thissleeve and is also formed along its outwardly turned underside with aseries of teeth or recesses 20.

A nonrotatable and axially fixed guide sleeve 11 is provided in each ofthe posts 1 and 2 and is formed with a boss 110 having a shoulder lldupon which the tubular hollow post rests. A screw 10 inserted throughthe wall of the post locks the respective sleeves in place. The screw 10thus limits the angular displacement of the sleeve 11 with respect tothe post and prevents the post from being lifted from the sleeve in theaxial direction.

The central bore 12 of each sleeve receives an actuating shaft l3forming part of the actuating element for the arresting mechanism. Atits lower end the shaft or pin 13 engages one arm of a Z-shaped bentplate 14 whose other arm or shank I4 is received between the free end ofa bifurcated leaf spring l5, l6 anchored to the fork 7 between the armsof the latter by a pin 19 via a pair of substantially U-shaped arms of abent member 18, the latter holding the leaf spring and the plate 14against lateral movement. The leaf spring comprises an upper leaf 16whose upwardly bent plank 16' engages the teeth to prevent rotation ofthe fork 7 relative to the sleeve 11 and thus with respect to the post.The lower leaf 17 has a shoe portion l7 adapted to frictionally engagethe periphery of the wheel or roller 6 thus, as the plate 14 is swung inthe counter-clockwise sense on the pin 19, it spreads the leaves of theleaf spring apart to arrest the fork and the roller. The leaves of theleaf spring are riveted at their other end 15. The assembly l4, 18, 19is located below the downwardly concave plate 21 forming the member 11b.

According to the invention, the shaft 13 is vertically shiftable in thepost and, as represented in FIG. 4, is connected to a piston-like slidebody 22 urged downwardly by a coil spring 23 seated against this slide.At its upper end, the spring 23 is seated upon a plate 24 anchored inthe post by inwardly bent rib 1a. The slide 22 is provided with atransverse bore 22' receiving the crank pin 25 traversing a verticallyextending slot 26 above the crossbar 3.

From FIGS. 1 through 4, moreover, it will be apparent that the pins 25are carried by the side plates or cheeks 27 of an actuating meansrepresented generally at 29 and forming a crank. The side plates 27 arejoined together-by a tubular connecting bar 28 bridging the posts 1 and2 and located wholly externally of the crossbar 3. It will be evidentalso that two such plates 27 and pins 25 are provided for thesimultaneous actuation of the arresting mechanism of both casters.

The connecting bar 28 is provided at its opposite end with a pair ofhandles 29 which, as shown in FIG. I, lead forwardly and laterallyoutwardly for easy manipulation by the patient. The bar 28 rides a pairof lowfriction rings 30, e.g. of polytetrafluoroethylene, which maybe'rotatable or fixed on the crossbar 3 at the ends thereof.

As can be seen from FIG. 4, each of the posts is formed with ahorizontal stub 3" onto which the tube 3 is pressfitted, the lattercarrying the rings 30. The handles 29' extend radially from the crossbar28 which actuates the rings 30 so that in one operating position the bar28 and the handle 29 engage rings 30 at locations A and B located on anopposite side of a plane P extending through the axis of the pins 25 andthe rings 30. As a consequence member 28 forms a simple crank with a'deadcenter position defined by the plane P through which the axis ofthe bar 28 may be swung. In that position, the actuating assemblies 28,29 cradle the ring 30 at each end of the crossbar 3 and the clutchformed by the handle portions. In this case, the axis of angulardisplacement of the actuating member coincides with the axis of thepins. Since the spring 23 urges the pin 25 downwardly, the actuatingmember is held in place against self or accidental displacement.

With the pin 25 held in its upper position (FIG. 2), the spring 23 iscompressed, the shaft 13 is also in its upper position and the plate 14is canted in its clockwise sense. The leaf springs 16 and 17 aredisengaged from the toothed rim 20 of plate 21 and from the periphery ofthe wheel 6 as described. When one or both handles 29 are lifted, theconnecting bar 28 shifts in the counterclockwise direction (FIG. 2) toclear the rings 30 and the crossbar 3. With such release of theactuating member, the spring 23 urges the slide 22 downwardly, likewisecarrying the pin in this direction and raising the handles into theposition shown in FIG. 3. Simultaneously, the shaft 13 is urgeddownwardly, thereby canting the Z-shaped plate in the counterclockwisesense and twisting the shank 14 of this plate between the leaf springs16 and 17. The leaf spring 16 is urged upwardly and engages the teeth 20to prevent rotation of theforce 7 whereas the leaf spring 17 is urgedagainst the periphery of the wheel 6 to prevent rotation of the latter.

To facilitate assembly of the actuating elements, an abutment bolt 31 isthread into the slide body 22 and extends between the spring seat 24 tohave a head 31 at its free end. The bolt 31 is screwed into the slidebody 22 to the extent necessary to maintain the transverse bar 22 alwayswithin the opening defined by the slot 26. This also limits the strokeof the spring 23 and prevents undue stress upon the leaf springs 16 and17. The pins 25 can then be inserted into the bores 22' withoutdifficulty and without requiring preassembly of the caster arrangement4.

ln FIGS. 5 7, l have shown another embodiment of the invention whereinthe spring 32 acts as a brakerelease spring, i.e. urges the shaft 113upwardly. In this embodiment, the coil spring 32 is seated at its lowerend against the guide sleeve 111 and bears, at its upper end, againstthe slide body 122. The shaft 113 is here threaded into the slide body122 to limit the stroke of the spring 32 and maintain the transversebore of the slide body in alignement with the slide 126.

The actuating bar 128 and its side plates 127 which carry the pins 125can engage the underside of the .nience of theuser. I g I 7 FIGS. 8 lillustrate another embodiment of the incrossbar 103 and its rings 130 inthe crotch from below in a kenematic reversal of the system shown inFIGS.

' 1 4. Inthis position, the shaft 113 is held downwardly mitted toapproach the crossbar' l03to relieve th'ear-' resting mechanism.

From FIG. 6 it can be seen that the connecting bar 128 maybe providedwith a furtherabutment29' handles of the ends thereof may be employed.It will be used equally well with a system in whichtlie spring opwhichmay be an extension of the actuating'arm 129 and can engage the ring 130from below at the location C..Thecontact with the bar 128 at location Dand of i the abutment 29 at the location C, inthe form of a furthercradle. retains the actuating armin its unlocked position as'illustratedin FlG. 6. As indicated in'broken '7 lines in FIG. 6, moreover, thehandle 129 may be pro vided on the opposite side of the bar 128 for theconvevention in which nondescribed portions. as in the case of FIGS. 7,correspond to those previously illuswhich operate the plate 14 etc. ofthe casters 204 are threaded into the slide body 222 while acoilspring'223 is provided between a spring seat 224 and the slide bodyabove the latter. The connecting bar 228: of the actuating mechanismhere bridges a pair of levers: 33 mounted on respective rings 30 atopposite ends of the crossbar 3. A hinge or articulation, 35eccentrically connects each lever 33 to a link 34 of semicircular configuration, the links 34 carrying the pins 225 which traverse the slots226 and engage the slide 222 as previously described.Adead-centerposition is'defined by the plane P between the axis of the crossbar 3and the axis of pins 225. The links 34 are semicircular segments adaptedto rest against the crossbar 3 and cradle the latter as shown in brokenlines in FIG. 8. Sincefthe force of spring 223 urges the pin 225downwardly and the links 34 entrain the pivots 35 similarly, with theaxis, E of the pins located to the letft of the plane R (dead centerposition), the actuating system is in a selfblocking condition. In thisposition,as in FIGQZ, the

shaft 223 relieves the locking arrangement and free movementof thecastis permitted. Note that the hanenabling the braketo be applied.

The arrangement of FIGS. 11 and l2is. of course. generally similartothat of FIGS. 8-'- 10except that the connecting bar 228 is replaced by asleeve 328'which bridges the two handle portions 13.3,whoselinks 13engage the pins 325 as previously described. The sleeve 328 is a pipecoaxial with the tube3. The pipe 328 is rigidwith respect to torsionstresses so that either of the tratedin. FIGS. 1 4.In thisembodiment5theshafts'2l3' understood that the systems of FIGS. 8 12 can'be erates to release the brake as described in connection with FIGS; 57. I V

I claim:

l. A steerable assembly comprisingiarpair of upright I transverselyinterconnected posts;

respective caster supports mounted on said posts for rotation aboutrespective upright axes; V respective rollers journaled on said supportsandrollingly carrying the assembly;

axially shiftable locking elements respectively mounted on said postsand operatively engageable I with the respective-supports for releasablyarresting said supports relativeto said posts and releasably arrestingsaid rollers relative; to said supports to immobilize said assembly; I 7H I a crossbar member interconnecting said posts;

an actuatingmember bridgingsaid posts externally of said crossbarmember, said actuating member being pivotally connected to said elementfor angular displacement with respect to anaxis transverse g V to saidupright axes between two positions with different spacings of saidtransverse axis from said crossbar member, said actuating memberengaging I said crossbar membertoggle-fashion against self displacementin one of said positions, one of said members being shiftable along saidposts generally in the direction of said upright axis; and

means connectingoneofsaidmembersw-i'thsaidelei ments for controllingsame upon angular displace ment of said actuating member between saidpositions.

7 r 2. The assembly defined in claim l and forming part of a wheel chairor the like wherein said one of said members is said said actuatingmember and said crossbar memberis fixed to. said posts. said actuating:mem

' slots.

3. The assembly defined in claim 2 wherein said actuating member has theconfiguration of a crankshaft 'lyingbetween said posts andcomprisesa'tran'sverse bar parallel to said crossbar member anda. pair ofeccentric g links fixed to the ends of said transversebar and providedwith said pins said transverse bar being -swingable betweensaidpositionsthrough adead-center position wherein the axis of saidtransverse bar, saidtrans f each of said posts, at least one brakeelement below eachsh'aft andengageable thereby for retaining the re-'spective support. and. roller against. mo ement, spring means in eachpost actingupon the respective shafts and urgingsaid actuating memberinto selfretaining engagement with said crossbar member in said one ofsaid positions: r

v 5. The assembly defined in claim 4. wherein said actuating member islocated above: said crossbar memben:

6. The assembly defined in claim 4 wherein said actuating member islocated below said crossbar member.

7. The assembly defined in claim 1 wherein said actuating membercomprises handle means rotatably mounted on said crossbar member, andlink means articulated to said handle means and engageablewith saidelements.

8. The assembly defined in claim 7 wherein said link means isarticulated to said handle means along said transverse axis and isconnected to said elements by a pair of pins defining a further axis,said handle means being swingable between said position through adeadcenter position wherein said further axis and said transverse axisare coplanar with said crossbar member.

9. The assembly defined in claim 8 wherein said crossbar member isprovided with a pair of bearing links at opposite ends thereof rotatablysupporting said handle means.

10. The assembly defined in claim 9 wherein said link means comprises apair of generally segmental links at opposite ends of said crossbarmember.

11. The assembly defined in claim 9 wherein said handle means includes asleeve surrounding said crossbar member and rotatable thereon.

12. A steerable assembly for a wheelchair comprising a pair of uprighttransversely interconnected posts;

respective caster supports mounted on said posts for rotation aboutrespective upright axes;

respective rollers journaled on said supports and rollingly carrying theassembly; axially shiftable locking elements respectively mounted onsaid posts and operatively engageable with the respective supports forreleasably arresting said supports relative to said posts and releasablyarresting said rollers relative to said supports to immobilize saidassembly;

a crossbar member interconnecting said posts;

an actuating member bridging said posts externally of said crossbarmember, said actuating member being angularly displaceable with respectto an axis transverse to said upright axes between two positions withdifferent spacings of said transverse axis from said crossbar member,said actuating member engaging said crossbar member toggle-fashionagainst selfdisplacement in one of said positions, one of said membersbeing shiftable along said posts generally in the direction of saidupright axis; and

means connecting one of said members with said elements for controllingsame upon angular displacement of said actuating member between saidpositions, said one of said members being said actuating member and saidcrossbar member is fixed to said posts. said actuating member beingprovided with at least one handle and forming therewith a bent lever,said posts being provided with respective slots parallel to therespective upright axes, said means connecting said one of said memberswith said elements including respective pins coupled with said actuatingmember and extending through said slots, said actuating member havingthe configuration of a crankshaft lying between said posts andcomprising a transverse bar parallel to said crossbar member and a pairof eccentric links fixed to the ends of said transverse bar and providedwith said pins, said transverse bar being swingable between saidpositions through a deadcenter position wherein the axis of saidtransverse bar, said transverse axis and said crossbar member aresubstantially coplanar, said posts being tubular, further comprising aguide sleeve mounted in each of the tubular posts and anchored thereinagainst rotation, said shafts each extending slidably and nonrotatablythrough the respective sleeve, said spring means being formed as a coilcompression spring, said shaft being provided with a slide block forminga seat for said coil compression spring, said pins extending throughsaid slots and engaging said slide blocks, said supports each beingprovided with an inwardly extending flange connected rotatably to therespective sleeveby a ball-bearing arrangement, said supports beingbifurcated and receiving the respective rollers between arms of thesupport being provided with a bifurcated leaf spring having a firstportion deflectable into engagement with the respective sleeve and asecond portion deflectable into engagement with the respective sleeveand a second portion deflectable into engagement with the periphery ofthe respective roller, and a Z-shaped member between the portions of therespective leaf spring and engageable by the respective shaft fordeflection of said portions. 7

13. A steerable assembly comprising a pair of upright transverselyinterconnected posts;

respective caster supports mounted on said posts for rotation aboutrespective upright axes;

respective rollers journaled on said supports and rollingly carrying theassembly;

axially shiftable locking elements respectively mounted on said postsand operatively engageable with the respective supports for releasablyarresting said supports relative to said posts and releasably arrestingsaid rollers relative to said supports to immobilize said assembly;

a crossbar member interconnecting said posts;

an actuating member bridging said posts externally of said crossbarmember, said actuating member being'angularly displaceable with respectto an axis transverse to said upright axes between two positions withdifferent spacings of said transverse axis from said crossbar member,said actuating member engaging said crossbar member toggle-fashionagainst selfdisplacement in one of said positions, one of said membersbeing shiftable along said posts generally in the direction of saidupright axis; and

means connecting one of said members with said elements for controllingsame upon angular displacement of said actuating'member between saidpositions, said actuating member comprising handle means rotatablymounted on said crossbar member, and link means articulated to saidhandle means and engageable with said elements, said link means beingarticulated to said handle means along said transverse axis and beingconnected to said elements by a pair of pins defining a further axis,said handle means being swingable between said position through adead-center position wherein said further axis and said transverse axisare coplanar with said crossbar member, said posts being tubular, and aguide sleeve mounted in each of the tubular posts and anchored thereinagainst rotation,

' said shafts each extending slidably and nonrotata-' bly through therespective sleeve, said spring a seat for said coil compression spring,said pins exblocks, said supports each being provided with an inwardlyextending flange connected rotatably to 7 means being formed'as a coilcompressionspring, said shaft being provided with a slide block'forming,

7 tending. through esaidaslotsr and engagingisaideslide the respectivesleeve by a ball-bearing arrangemenLsaidsjupports being bifurcated andxeceivifng; the' respective rollers between: armsiofth'esu pport, eachsupport be-ingiprovided' with a bifurcated leaf;-

spring having a first portion vdeflectable into engagement with therespective sleeve and asecond f1 portion 'deflec'table into engagementwith the pei riphery of the respective roller; and a Z-shaped memberbetween the portions of the respective leaf 1 spring and engagea'ble' bythe respective shaft-"for deflection of said portions. a

